Arrow spines

Hello again everyone!!
Arrow spines confuse the he11 out of me. This is annoying because I intend to move up my draw at Christmas, and I will be going from 38 on the fingers to 42 or 44 depending on what limbs I can find in stock at the right money. From what I can tell on the spine charts, this is close to the "border" between spines. I am wondering, if I stick with existing arrows (which I think would then be deemed "too soft" but I don't know if spines go up or down in stiffness as your draw goes up) am I likely to notice much of a problem? I mean, if they're going to be "too soft" at 42 they must be "almost too soft" at 38 so how would I know whether changes in the groups are down to the arrows or down to me adjusting to new draw? Do "too soft" spines run one way and "too stiff" the other? I shoot right handed, is there anything particular that I should be looking out for?
Cheers!!
 


malbro

Instinctive Archer
Supporter
Hi
The recommended spine for a given draw weight varies with draw length and type of bow, compound or recurve, not sure about longbow as that is not my forte. Spine tables give different recommended spine for 38, 42 and 46, the change takes place at 40 and 45, tables are also different depending on the type of arrow so difficult to say more without additional information.
Draw length, type of bow, type of arrow (carbon, ali etc)
 


LionOfNarnia

Supporter
Supporter
Yes! Spines were designed to baffle & frustrate us, it's witchcraft I tell 'e!
I made a similar ~ move a couple of weeks ago, still trying to decide if the old 600's still work or the new 500's are better.
If it's close, maybe there's enuff adjust in the plunger to sort it out.
But there's no magic formula, ya just 'suck it & see'.
 


My ACCs have 3-04 / 680 written on the shaft. I know that is something to do with the spine but don't know what it means. I have been told that they are fairly soft for 29.5" knock groove to base of point and 42lbs. I don't understand enough about arrow stiffness / softness to know what to look out for when shooting them. I think a long time ago I was old something like "for right handed archer spines go left when they are too soft" but I really can't remember. I have stared at the spine charts for quite a long time know but no matter how hard I stare, I still can't make sense of the numbers.
 


LionOfNarnia

Supporter
Supporter
They sound soft, WDY get a few ready-mades in the 470-620 range & see what suits you best? No need to spend a fortune, even Mybo Hailstorms will do the job at less than a tenner each, available singly.
 


Rik

Supporter
Supporter
The numbers aren't particularly relevant. That's why we use charts. You can have the same numbers on different makes of shaft (even supposedly measured the same way) with different results. The actual "spine" number is a measure of stiffness and it's the distance an example of the shaft bends, when you hang a weight from the middle. Which is why people talk about a shaft being "too stiff" or "too soft". The numbers get bigger for a weaker shaft, because it represents the amount of bend - more deflection, bigger number. But the bit not usually explained is that "stiffness" is not the thing which determines whether the shaft matches your setup. It's just something that's relatively easy to measure and is indirectly related to the important thing: when the shaft bends as you release it. It's not of immediate importance how much the shaft bends, but when it bends determines whether your clearance is good or not.

The trick is that stiffer shafts (of a particular model) bend quicker than weaker shafts (of the same model). So if your shaft is not bending quickly enough, it's moving forwards quicker than it is bending (say the bow is stronger, faster, than that shaft is made for), then you need a stiffer shaft because it will bend quicker. Bend in the right place to clear the bow.
 


So... if the arrow doesn't bend quickly enough and hits the riser then it would land... left? Assuming right handed archer. It'd be like a ricochet off the riser wouldn't it?
 


geoffretired

Supporter
Supporter
Usually a soft arrow hits the riser with its back end, which pushes the back away from the riser( to the left for a right handed archer) The front end is well clear of the riser by then. The contact can be heard, usually, and it makes the arrows fly badly at the start .
 


Rik

Supporter
Supporter
Yes... Though clearance issues can be maddeningly difficult to analyse and clear up... Because variations in the shot can lead to shafts with edgy clearance hitting more or less, or not at all.. So groups open up without obvious noise (if it's just the fletches hitting)... And if it's the fletches hitting you can find really misleading results from bareshafting.
 


malbro

Instinctive Archer
Supporter
I recently bought an Andy Soars Blackbrook Carbon TDR C, now Andy does not talk about spine when he recomends arrows instead he quotes a figure of 8 to 9 grains per pound of draw for his bows. For example for a 40lb draw he recomends arrows weighing between 320 and 360 grains, he used to quote an absolute minimum of 7 grains per pound but when I emailed him recently he suggested 8 grains was better.

I have some 5.5mm OD carbons which weigh 289grains all up and his suggestion was that they were too light and could cause damage to the bow no mention of spine at all.

So is this a restriction on more traditional bows with wooden risers and spine is still relevant but restricted to arrows of the right weight?
 


Timid Toad

Moderator
Staff member
Supporter
Fonz Awardee
Ironman
Usually a soft arrow hits the riser with its back end, which pushes the back away from the riser( to the left for a right handed archer) The front end is well clear of the riser by then. The contact can be heard, usually, and it makes the arrows fly badly at the start .
So can an overly stiff arrow.
 


AndyW

Active member
I recently bought an Andy Soars Blackbrook Carbon TDR C, now Andy does not talk about spine when he recomends arrows instead he quotes a figure of 8 to 9 grains per pound of draw for his bows. For example for a 40lb draw he recomends arrows weighing between 320 and 360 grains, he used to quote an absolute minimum of 7 grains per pound but when I emailed him recently he suggested 8 grains was better.

I have some 5.5mm OD carbons which weigh 289grains all up and his suggestion was that they were too light and could cause damage to the bow no mention of spine at all.

So is this a restriction on more traditional bows with wooden risers and spine is still relevant but restricted to arrows of the right weight?
I don't know a thing about wooden arrows but as the bowyer he is recommending a minimum gpi to avoid too much shock to the bow which would damage it, much the same as dry firing. Regarding arrow weight: wrt weight most carbons will fall in the range of 7+ gpi irrespective of stiffness so that needs to be a minimum then look to spine rating. It's not really an issue for adult compounds (which is me) as the gpi will always be over the minimum, but I do go as light with arrows as I can sensibly.
P.S. That's just me trying to get fast arrows as I shoot field - if I shot target I would go heavier and skinny for outdoor to avoid drift and avoid the arrows dropping off at distance - light arrows will really slow up past 50/60 yrd especially with something like blazer vanes or feathers.
It's all a trade off - what's the most important factor to you? Unless you've been doing it a while and fancy getting a bit saucy stick with the herd.
I shoot 7.4gpi 400s at 29inch with a conquest 4 but 6.9gpi 500s at 26.25inch with an overdraw out of my old Martin - for the C4 I'm bothered about the limbs, the other I'm not, if they split happy days I will buy a set of Barnsdale limbs which I've wanted to put on it for years.
 


Last edited:
Top